nmap with awk output

awkmap.md

nmap -v -sn 192.168.10/25 -oG - | awk '/Up$/{print $2}'

nmap Options Explained

nmap: The network mapper tool, used for scanning hosts and networks.

-v: Enables verbose output, giving more detail during the scan.

-sn: Stands for "ping scan" — it disables port scanning and only checks which hosts are up (i.e., responding to ping or ARP).

192.168.10.0/25: This is a CIDR subnet notation. It scans IPs from 192.168.10.0 to 192.168.10.127 — a total of 128 addresses.

-oG -: Outputs results in grepable format (-oG) and sends it to stdout (-), rather than a file.

nmap -v -sn 192.168.10.0/25 -oG - | awk '/Up$/{print $2}' | while read ip; do echo -n "$ip "; nslookup "$ip" | awk '/name =/{print $4}'; done

Added hostname lookup

while read ip; do ... done: Loops through each IP found to be up.

nslookup "$ip": Resolves the hostname for each IP.

awk '/name =/{print $4}': Extracts the canonical hostname from nslookup output.

bash function

scan_hosts() {
  local subnet="$1"
  if [[ -z "$subnet" ]]; then
    echo "Usage: scan_hosts <subnet>"
    echo "Example: scan_hosts 192.168.10.0/25"
    return 1
  fi

  echo "Scanning subnet: $subnet"
  nmap -v -sn "$subnet" -oG - | awk '/Up$/{print $2}' | while read ip; do
    hostname=$(nslookup "$ip" 2>/dev/null | awk '/name =/{print $4}')
    printf "%-15s %s\n" "$ip" "${hostname:-<no hostname>}"
  done
}

Parallelize for Speed

scan_hosts() {
  local subnet="$1"
  if [[ -z "$subnet" ]]; then
    echo "Usage: scan_hosts <subnet>"
    echo "Example: scan_hosts 192.168.10.0/25"
    return 1
  fi

  echo "🔍 Scanning subnet: $subnet"
  nmap -sn "$subnet" -oG - | awk '/Up$/{print $2}' | while read -r ip; do
    # Resolve hostname (fallback to <no hostname> if not found)
    local hostname
    hostname=$(nslookup "$ip" 2>/dev/null | awk -F'= ' '/name =/{print $2}' | sed 's/\.$//')
    printf "%-15s %s\n" "$ip" "${hostname:-<no hostname>}"
  done
}

Use in conjunction with:
ip -4 -br a | grep Up

ip: the modern replacement for ifconfig, used to show/manipulate network interfaces.

-4: restricts output to IPv4 addresses only.

-br (short for --brief): gives a concise, tabular output.

a (short for address): shows IP address information for all interfaces.

| grep UP

|: pipes the output of the previous command into the next.

grep UP: filters lines that contain the word UP, which indicates that the interface is active and running.